Robots are widely utilized in industrial assembly line and other manufacturing applications to perform repetitive tasks very precisely without the need for human operation, interaction, or supervision. For example, robots are commonly used in the automotive industry to perform a number of tasks such as material handling, cutting, welding, and the like.
To amortize the considerable cost of an industrial robot over a variety of tasks, the robot arm is typically separate from a diverse array of robotic tools, which are removably attached to the end of the robot arm. Different tools are removably attached in such a way through use of a tool changer. The tool changer consists of a body for mechanically attaching the robot arm to a tool and one or more utility modules connected to that body for passing various utilities, such as electrical power, between the robot arm and the tool. Specifically, one half of the tool changer body, called the master module, is permanently affixed to the robot arm. The other half, called the tool module, is affixed to each tool that the robot may utilize. When the robot arm positions the master module adjacent the tool module connected to a desired tool, the master module actuates a coupler to mechanically attach the master and tool modules together.
With the master and tool modules so attached, utility modules may provide for the passing of utilities between the robot and a tool. For example, a master electrical signal module may be affixed to the master module and a tool electrical signal module may be affixed to the tool module. The master electrical signal module includes electrical contacts that mate with those of the tool electrical signal module when the master and tool modules are coupled together. With these electrical contacts mated, electrical power is transferred from one or more power supplies, across the master and tool electrical signal modules, and made available at the tool.
Design restrictions of many tool changer applications dictate that electrical power transferred to the tool electrical signal module must be shared with the master electrical signal module (i.e., the master electrical signal module and the tool electrical signal module must use the same one or more power supplies). Accordingly, because the master electrical signal module must provide electrical control signals to the master module for actuating the coupler, the one or more power supplies must remain on during the coupling and uncoupling of the master and tool modules. As a result, transient electric arcs form across the electrical contacts of the master electrical signal module and the tool electrical signal module during the coupling/uncoupling process. Especially when high inrush current exists, arcing accelerates the wear of the contacts and thereby diminishes the contacts' electrical life below their mechanical life.
Various methods are known to mitigate damage to the electrical contacts caused by arcing. Improving the material composition of the electrical contacts, for example, permits the contacts to better withstand the strain of arcing. These methods, however, merely prolong the electrical life of the contacts (e.g., to a point still short of their mechanical life) because arcing still occurs.